If you cleaned it it will need to acclimate back to your system before it starts pulling out gunk. Usually about a week or so depending on how established your aquarium is. I clean my cup but never my base. It also houses beneficial bacteria within your sump so I don’t like disturbing the ecosystem it has created. Just my opinion and what I do.
Id take it back apart and make sure your impellars correct and in all the way. Im guessing you couldnt get the cover on it otherwise.
Did you restart the pump a cpl times to see if it got more water?
Its in pretty deep water. Your drain tube is.open all the way?
The air looks good.
Lift the unit up and see if the water level in the skimmer drops or rises. If it drops, add more water to the sump. Also blow thru the muffler tube on top (the white tube from unit in your pic) which may be restricted.
You got to love my x-ray eyes. Funny even a drunk falls down on a 20 dollar bill once in his lifetime. The truth is I was confusing my Aqua Maxx skimmer with the white thingy with my Simplicity without the white thingy LOL.